What was so astonishing about Gentiles being saved without becoming Jewish proselytes?
The Jewish believers were astonished because this was the first instance of Gentiles being saved. Until then, Gentiles had not been saved apart from the ritual of Judaism and proselytizing. The Holy Spirit fell on Gentile believers while Peter preached, proving their faith was accepted without their becoming Jewish proselytes.
Les explains that the astonishment in Acts 10:45 is important. If Gentiles had been saved for the previous six, seven, or eight years, why would they be astonished? But they had not been; this was the first instance. It was an astonishing fact that Gentiles could be saved without adhering to the ritual of Judaism, proselytizing, and all the rest of it. They believed, the Holy Spirit manifested their faith, and then Peter had to hurry to baptize them.
And they of the circumcision which believed were astonished, as many as came with Peter, because that on the Gentiles also was poured out the gift of the Holy Ghost.
When they heard these things, they held their peace, and glorified God, saying, Then hath God also to the Gentiles granted repentance unto life.
More Questions
What happened to the circumcised Jewish believers with Peter in Acts 10:45 when the Holy Spirit fell on the Gentiles?
The six circumcised Jewish believers who came with Peter were astonished when they saw the Holy Spirit falling on the Gentile listeners, even though they already believed that Jesus is the Christ.